Japanese Unexamined Patent Application Publication No. 2004-7345 discloses a chip antenna in which a feeding electrode and a non-feeding electrode are arranged on a dielectric substrate so as to face each other with a predetermined distance therebetween. FIG. 1(A) is a six-surface diagram of the chip antenna disclosed in Japanese Unexamined Patent Application Publication No. 2004-7345, and FIG. 1(B) is an equivalent circuit thereof.
Referring to FIG. 1(A), a feeding electrode 34 is formed on the bottom surface, fourth side surface, and top surface of a dielectric substrate 31 shaped like a rectangular parallelepiped. Similarly, a non-feeding electrode 36 is formed on the bottom surface, the third side surface, and the top surface. The feeding electrode 34 and the non-feeding electrode 36 are formed so as to face each other with a predetermined distance therebetween on the top surface of the dielectric substrate 31.
Referring to FIG. 1(B), the feeding electrode 34 and the non-feeding electrode 36 are coupled to each other as a result of the open ends thereof facing each other with a predetermined distance therebetween. Thereby, wide-band characteristics are obtained.
However, in the existing chip antenna disclosed in FIG. 1(A), where a chip antenna 30 is mounted in a non-ground area of a circuit substrate, since the resonant frequency of the antenna strongly depends on a positional relationship between the antenna and the ground electrode on the circuit substrate, the resonant frequency of the antenna needs to be adjusted by, for example, changing the area of the non-ground area, in accordance with the surrounding environment, such as other mounted components and the casing close to the mounting area of the chip antenna on the circuit substrate. Hence, there has been a problem in that the area of the non-ground area cannot be fixed.